Cored wire electrode having 200 to 2000 ppmo{11

ABSTRACT

A hollow tubular sheath containing manganese and silicon ingredients with iron powder, the total wire chemistry containing between 200 and 2000 parts per million oxygen.

United States Patent [191 Kubli et al.

[ Dec. 11, 1973 CORED WIRE ELECTRODE HAVING 200 TO 2000 PPMO [73]Assignee: Union Carbide Corporation, New

York, NY.

[22] Filed: Dec. 27, 1971 [21] Appl. No.: 212,756

[52] US. Cl 219/146, 117/202, 117/207,

148/26, 219/73, 219/126 [51] Int. Cl B23k 35/22 [58] Field of Search148/26; 29/1912,

[56] References Cited UNITED STATES PATENTS 3,394,238 7/1968 Wilcox219/146 3,424,892 1/1969 Wilcox 219/146 3,218,432 l1/l965 Peck 219/145Primary Examiner-J. V. Truhe Assistant ExaminerGeorge A. MontanyeAttorney-Paul A. Rose et a1.

[5 7] ABSTRACT A hollow tubular sheath containing manganese and siliconingredients with iron powder, the total wire chemistry containingbetween 200 and 2000 parts per million oxygen.

5 Claims, No Drawings CORED WIRE ELECTRODE HAVING 200 TO 2000 PPMO Thisinvention relates to consumable electrodes for electric welding and,more particularly, to a cored wire electrode, sometimes referred to as atubular electrode, for welding in a method utilizing a welding fluxcomposition.

The electroslag method of welding metals is becoming more widely used inindustry. Up until now, in most applications solid consumable wires havebeen used with the electroslag flux materials. One problem, however, hasbeen the difficulty in achieving consistently good weld impactpropreties with solid wires. It was discovered that a tubular electrodehaving a core of metallic ingredients as specified hereinafter producedconsistently good weld impact properties; that is, the weld metalproperties consistently exceeded AWS minimum standards of 15 ft-lbs.C.V.N. at F. in mild steels such as 197] ASTM. A-36 and A-441 which havethe following nominal compositions: A-36; carbon .26 max.; manganese0.80-1.20; Si 0.15-0.30; balance iron. A-441; carbon 0.22 max.;manganese 0.85-1.25; Si 0.30 max.; copper 0.20 min.; balance iron.

Accordingly, it is the main object of this invention to provide aconsumable electrode wire having a core of metallic ingredients in amild steel sheath.

It is another object to provide such a wire for use in welding methodswherein a welding flux is utilized.

Another object is to provide such a wire for electroslag welding.

Yet another object is to provide a metallic core wire for use inelectroslag welding of mild steels which will consistently produce weldshaving impact properties in excess of ft-lbs. C.V.N. at 0 F., whilemaintaining strength, ductility and bend requirements.

' These and other objects will become apparent from the followingdescription and examples which are provided to illustrate to one skilledin the art the concept of the invention.

While the description and examples are primarily directed to theelectroslag method of welding, it is to be understood that the coredwire of this invention may also be utilized in the submerged arcprocess.

Flux cored wires are well known in the art. Such wires usually containfluxing materials such as oxides, carbonates, etc., in addition tometallic elements. The wire of this invention can be characterized as ametal core wire since it contains only metals in the core material. Thecore material is preferably composed of manganese metal, ferrosilicon,which is 50 percent iron and 50 percent silicon and iron powder.

It has been found that in order to achieve the mechanical propertiesdesired in the weld metal and specifically the impact propertiesdesired, the oxygen content of the wire must be kept below about 2000ppm. Accordingly, the iron powder which usually is the main contributorof oxygen in a core wire should be controlled or carefully selected inorder that the wire not exceed 2000 ppm oxygen. Cored wire compositionshaving greater than 2000 ppm resulted in welds which were below the 15ft-lbs. C.V.N. impact properties required for mild steels by the AWSstandards. Oxygen contents in excess of 2000 ppm also have a deleteriouseffect on other mechanical properties such as strength, ductility andbend properties. It is theorized that the oxygen content of the wireshould not be below 200 ppm in order to achieve active oxidation ofelemental manganese and silicon in the weld puddle to scavengeimpurities such as sulfur or tie them up in a harmless form.

The chemical analysis of the cored wire of the invention, in itsbroadest aspects, based on the total weight of the electrode isgenerally as follows: about 0.05 to about 0.12 percent carbon; about 1.2to about 2.4 percent manganese; about 0.20 to about 0.50 silicon; andthe balance iron, with the oxygen content between about 200 ppm and 2000ppm. The above chemical analysis for carbon, manganese and silicon wasdetermined by a standard wet chemical analysis technique described byASTM E 30-70. The oxygen analysis was determined by Fast NeutronActivation Analysis.

The above chemical analysis can be achieved with a 20 weight per centcore containing the following ingredients: about 4.5 to 10.5 core weightpercent of manganese; about 1.0 to 2.5 core weight percent silicon; andthe balance iron powder, the oxygen content of the wire being about 1000ppm.

A typical composition for the wire of the invention with 20 percent coreis as follows: carbon 0.07 weight percent; manganese 1.90 weightpercent; silicon 0.35 weight percent; the balance iron, the wire havingbetween about 200 ppm and 2000 ppm oxygen.

In a preferred form of the invention, a mild steel sheath has a corewhich is 20 weight per cent of the total electrode and which contains7.9 core weight percent manganese; about 33 core weight percentferrosilicon, which provides 1.65 core weight per cent silicon and thebalance iron powder; the total oxygen content of the wire being about1000 ppm.

It should be understood that the core weight per cent may be varied,preferably between 10 and 40 weight percent of the total electrode andthe composition of such core varied accordingly to produce the overallwire chemical analysis and oxygen content hereinabove set forth anddefining the scope of the invention.

Having described the invention in a general way and with respect tocertain preferred embodiments, the following Examples and data areprovided so that those skilled will know how to practice the invention:

EXAMPLE I A wire A consisting of a mild steel sheath and a twenty (20)weight percent core t 2 percent had an overall wire chemistry of carbon0.08 weight per cent; manganese 1.70 weight percent; silicon 0.26 weightpercent; balance iron mainly in the form of iron powder in the core. Theoxygen content was 780 ppm.

Test welds were made using the electroslag process with a flux materialidentified and sold under the trade name as Linde 124 containing about15-25 weight per cent CaO; 12-18 weight percent CaF 5-15 weight percentMgO; 25-40 weight per cent SiO and 10-20 weight percent Al,O Consumableguide tubes were used, coated with a similar flux material. The weldswere made at 550 amps d.c.r.p. at 35-36 volts. The base materials wasA-44l, defined above.

Mechanical properties were as follows: 56,400 psi yield strength; 77,400psi ultimate tensile strength; 29.4 percent elongation in 2 inch gaugelength. The impact values were 29.2; 38.5; 32.9; 33.1 and 19.3 ft-lbs.C.V.N. at 0F. which give an AWS average of 31.7 ft lbs. C.V.N. at 0F.The welds also passed the guided side bend tests.

EXAMPLE n A wire B was used in this Example. This wire had theMechanical properties were as follows: 53,200

yield strength; 80,100 ultimate tensile strength; 26.9

elongation in a 2 inch gauge length. The impact values were 28.6; 32.5;21.9; 33.3; 30.4 ft-lbs. at F. which gives an AWS average of 30.5ft-lbs. C.V.N. at 0F. The welds also passed the guided side bend tests.

EXAMPLE 111 EXAMPLE IV In this test a solid wire having carbon of 0.08weight per cent; manganese of 1.24 weight percent; silicon of 0.32weight per cent and an oxygen content of less than 100 ppm was usedunder identical welding conditions to those set forth in Example I. Theyield strength of the weld metal was 51,100 psi. The ultimate tensilestrength was 71,600 psi. The elongation was 28.5 percent. The impactswere 16, 16, 16, 17 and 24 ft-lbs. C.V.N. at 0F. which gives an AWSaverage of 16.3 ftlbs. C.V.N. This same wire used in many more testsactually produced impact values which fifty per cent of the time werebelow ft-lbs. C.V.N. at 0F. 1f a wire does not consistently, by which ismeant one hundred percent of the time, meet the AWS minimum standard,the wire cannot be qualified.

Many tests with other solid wires such as AWS- E70S-3 and AWS-EM-l3Khaving similar compositions to that of the invention produced weld metalwhich would fail to meet the standard setup by the American WeldingSociety (AWS). For example, AWS- E70S-3 wire which usually containscarbon 0.06-0.15; manganese 0.90-1.40 and silicon 0.45-0.70 producedweld metal having impacts ranging from 1 l to 30 ft-lbs. C.V.N. at 0F.AWS-EM-13K wire which usually contains 0.07 to 0.19 carbon; 0.90 to 1.40manganese and 0.45 to 0.70 silicon produced weld metal having impactsranging from 8-22 ft-lbs. C.V.N. at 0F.

The above data indicates that a cored wire having an oxygen content offrom 200 ppm to 2000 ppm will consistently produce impact properties inweld metal in excess of 15 ft-lbs. C.V.N. at 0F. in mild steel metal. Onthe other hand, solid wire will only, by chance, occasionally produce aweld having satisfactory impact values. It is postulated that a reasonfor improved mechanical properties when using a cored wire havingessentially the same chemistry as a solid wire with the exception thatoxygen content is maintained in a critical range may be the type ofmetal transfer obtained with a cored wire in electroslag welding. Coredwire produces smaller droplets in the molten puddle which results in adifferent solidification pattern in the weld metal from that obtainedwith solid wire. Solid wires produce large globular droplets of metal.The difference in solidification patterns are believed to affect themechanical properties.

Having described the invention in general and specific terms, it shouldbe understood that minor modifications, not specifically referred to,may be made without departing from the spirit and scope of theinvention.

What is claimed is:

l. A consumable wire electrode comprising a hollow sheath of mild steeland a core material comprising from about 10 to about 40 weight percentof the total electrode, the total wire chemistry being composed of 0.05to 0.12 weight percent carbon; 1.2 to 2.4 weight percent manganese; 0.20to 0.50 weight percent silicon; oxygen between about 200 ppm and 2000ppm and the balance iron, including iron powder in the core.

2. A wire according to claim 1 wherein the core material is about 20weight percent of the total electrode.

3. A wire according to claim 2 wherein the core material consists ofabout 4.5 to about 10.5 core weight percent manganese; about 1.0 toabout 2.5 weight percent silicon; oxygen about 1000 ppm and the balanceiron powder.

4. A wire according to claim 3 wherein the manganese is about 7.9 coreweight percent, the silicon is about 1.65 core weight percent; and theiron powder is the balance of the core weight percent.

5. A consumable wire electrode comprising a hollow sheath of mild steeland a core material comprising 20 weight percent of the total electrode,the total wire chemistry being composed of 0.07 weight percent carbon;1.90 weight percent manganese; 0.35 weight percent silicon; oxygenbetween about 200 ppm and 2000 ppm and the balance iron, including ironpowder in the core.

2. A wire according to claim 1 wherein the core material is about 20weight percent of the total electrode.
 3. A wire according to claim 2wherein the core material consists of about 4.5 to about 10.5 coreweight percent manganese; about 1.0 to about 2.5 weight percent silicon;oxygen about 1000 ppm and the balance iron powder.
 4. A wire accordingto claim 3 wherein the manganese is about 7.9 core weight percent, thesilicon is about 1.65 core weight percent; and the iron powder is thebalance of the core weight percent.
 5. A consumable wire electrodecomprising a hollow sheath of mild steel and a core material comprising20 weight percent of the total electrode, the total wire chemistry beingcomposed of 0.07 weight percent carbon; 1.90 weight percent manganese;0.35 weight percent silicon; oxygen between about 200 ppm and 2000 ppmand the balance iron, including iron powder in the core.